Electro hydraulic control mechanism



April 5, 1960 w. E. RENICK ETAL 2,931,388

ELECTRO HYDRAULIC CONTROL MECHANISM Filed Dec. 30, 1953 2 Sheets-Sheet 1INVENTORS FIG 1 WENDELL E. RENIGK KENNETH c. GOODMAN April 5, 1960 I w.E. RENICK ETAL 2,931,388

ELECTRO HYDRAULIC CONTROL MECHANISM Filed Dec. 30, 1953 2 Sheets-Sheet 2Y INVENTORS 5O WENDELL E. RENICK I;(ENNETH G. GOODMAN 2,931,388 ELECTROHYDRAULIC CONTROL MECHANISM Wendell E. Renick and Kenneth C. Goodman,Columbus, Ohio, assignors, by mesne assignments, to American Brake ShoeCompany, New York, N.Y., a corporation of Delaware Application December30, 1953, Serial No. 401,176 8 Claims. (Cl. 137623) This inventionrelates generally to hydraulic apparatus and more particularly tocontrol valve mechanism for hydraulic motors and actuating means forsuch control valve mechanism.

An object of this invention is to provide a control valve mechanism andactuating means therefor which will make a more accurate governing ofthe operations of a hydraulic motor possible.

Another object of this invention is to provide a control mechanism for ahydraulic motor which will utilize the movement of a portion of themotor to assist in governing the operation of the motor, another elementoperating according to a predetermined pattern working in conjunctionwith the portion of the motor to the end that desired operations may beautomatically performed.

A further object of the invention is to provide a novel control valvemechanism having electronically governed pilot means which in turncontrols the operation of main valve means and effects the substantiallyinstantaneous response of the motor to control signals irrespective ofthe manner in which they are transmitted to the system.

A still further object of the invention is to provide a control valvemechanism having a main valve for selec tively controlling the operationof a reversible fluid motor, flow control means for determining thepressures of the fluid supplied to the fluid motor andelectro-responsive pilot valve means for effecting the operation of themain valve, suitable electrical circuit means being provided to energizeand de-energize the electro-responsive means.

Another object of the invention is to provide a novel circuitarrangement for electronically controlling the pilot valve portion ofthe control valve mechanism mentioned in the preceding paragraph so thatthe fluid motor may be caused to perform according to a predeterminedpattern or plan and to automatically repeat such pattern of operationsas many times as desired.

An object or" the invention also is to provide the electronic controlcircuit mentioned in the preceding paragraph with an electrical deviceknown as a null bridge and to connect part of such device with a movableportion of the reversible fluid motor and another part with means formoving it according to a predetermined plan, such movement serving tocause an unbalance of the null bridge which in turn directs a signal tothe pilot control mechanism making it cause the fluid motor to operateto restore the balance of such null bridge; due to the use of theelectronic control circuit extreme sensitivity, speed and accuracy ofoperation of the fluid motor will be secured.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being bad to the accompanyingdrawings wherein a preferred form of embodiment of the invention isclearly shown.

In the drawings:

Fig. 1 is a diagrammatic view of the hydraulic circuit having areversible fluid motor and a control valve mechanism formed inaccordance with the. present invention innited States Patent corporatedtherein; the view also showing the electrical circuit for operating thecontrol valve mechanism.

Fig. 2 is a vertical longitudinal sectional view taken through thecontrol valve mechanism shown in Fig. 1.

Referring more particularly to the drawings, numeral 21 designates areversible fluid motor. In the present instance, the motor 21 is of thepiston and cylinder type, the cylinder being indicated by the numeral 22and the piston by the numeral 23. This piston has a ram 24 projectingtherefrom through one end of the cylinder 22. Fluid motors of this typeare employed where reciprocatory motion is desired and are particularlyemployed in hydraulic presses.

The reversible fluid motor 21 is arranged in a hydraulic circuitdesignated generally by the numeral 25. This circuit has a source offluid pressure including a reservoir 26, a motor driven pump 27 and arelief valve 28. These elements may be of any desired form and are onlydiagrammatically illustrated. The hydraulic circuit also includes acontrol valve mechanism forming part of the subject matter of thisinvention, this mechanism being designated generally by the numeral 30.A fluid pressure line 31 extends from the pressure source to the controlvalve mechanism 30 and an exhaust line 32 extends from the valve back tothe reservoir. Forward and reverse motor lines 33 and 34 also extendfrom the control valve mechanism to the reversible fluid motor 21. Thecircuit further includes a pilot pressure line 35 leading from theoutlet of the pump 27 to the upper portion of the control valvemechanism. This pilot pressure line 35 is provided with a pressurereducing valve 35A to limit the pressure supplied to the pilot controlmechanism.

The control valve mechanism 30 is shown in detail in Fig. 2. From thisfigure, it will be observed that the control valve mechanism includes abody 36 and a pair of end caps 37 and 38. The body is provided with amain spool bore 40 having a plurality of annular grooves 41 to 45,inclusive, communicating therewith. In the form of the inventionillustrated, the bore is enlarged at one end as shown at 46. The purposeof this enlargement will be set forth hereafter. Ports 41 and 42constitute inlet ports and are connected by passages 47 and 48 with theinlet port 50, this port being connected with the line 31 leading fromthe fluid pressure source. Body 36 also has a pair of chambers 51 and 52formed therein, these chambers communicating with the passages 47 and48. The chambers may be formed in any desired manner; they are separatedby a partition 53. The passages 47 and 48 are divided into sections bythe chambers 51 and 52, certain sections of the passages communicatingwith the port 50 and the other sections communicating with the grooves41 and 42. The points of communication of these sections with thechambers 51 and 52 are longitudinally spaced. The chambers are providedwith inserts 54 which form valve seats 55 between the points ofcommunication of the passage sections with the chambers. These valveseats cooperate with valve portions 56 of piston valves 57 which aredisposed for sliding movement in the sleeves 54. These piston valvesconstitute flow control valve elements in the operation of themechanism. Grooves 43 and 44 formed in the body 36 are connected byports 58 and 60 with the lines leading to the reversible fluid motor.Port 60 constitutes the forward motor port while 36 connect these ports58 and 60 with the inner ends of the chambers 51 and 52. The purpose ofthis connection said grooves providing spaced heads 64, 65 and 66. The

will be made apparent in the following description.

The main valve bore 40 has a main valve spool 61 disposed for slidingmovement therein, this spool having a pair of spaced grooves 62 and 63formed in the side wall,

. sume its centered position.

length of the 'g'roovesis such that, when the spool is cen- 40-to port45 which constitutes the exhaust port, this port being connected by line32 with the reservoir '26. Spool 61 is normally biased toward thiscentered position'by'coil springs 67 arranged between the ends of thespool and the end caps 37 and 38. End cap 37 has an adjusting screw 68threaded therethrough for adjusting the tension of the spring 67. Spool61'is pilot operated being controlled by a pilot valve indicatedgenerally by the numeral 70. This pilot control valve is disposed in theupper portion of the valve casing 36, a bore 71 extending through thebody 3 6 to receive this pilot valve. The end ;caps 37 and 38 havepassages 72 and 73 formed therein to establish communication between theends of the bore 71 and the main spool bore 40. Bleed passages 74 alsoconnect the passages 72 and 73 with the exhaust port 45. g The pilotvalve mechanism includes a spool 75 having spaced heads 76 adjacent thecentral portion and valve stems 77 and 78 extending in oppositedirections from the heads 76. These stems are tapered at their outerends to form metering valves 80, these metering valves 80 cooperatingwith orifices 81 provided in plugs '82 disposed in the ends of the bore71. The stems 77 and 78 extend through central openings inelectromagnetic windl lugs 83 and 84, these windings being positioned inthe bore 71 between the plugs 82 and the heads 76 of the valve spool 75.Since the valve spool is in effect a one'piece unit, movement in eitherdirection in the bore 71 will simultaneously increase the effective sizeor area of the orifice'at one end and decrease the etfective size 'orarea of the orifice at the other. The flow of pilot fluid pressure "tothe main valve spool will thus be controlled. Heads 76 of spool 75 areprovided withorifices 85 to permit flow of fluid from the pilot pressureinletrport 86 'tothe passages 72 and 73 leading to the ends of themain'valve bore40.

Due to the provision of the orifices 85, valve spool 75 operates as aflow divider, the orifices 85 creating a pressure diiferential betweenopposite ends of the heads 76. As long as the valve spool 75 is centeredlongitudinally in the bore 71, the effective size of the orifices 81will be equal and pressure at opposite ends of the valve spool'75 willalso be equal. The valve'spool 75 will then be dis posed in itslongitudinally centered position. 'If either coil 84 M85 is energized, amagnetic force will be created which will cause the spool 75 to move inresponse to this magnetic force. When the spool moves in this manner,one of the orifices 81 will be reduced in eflective size while the otherwill be increased. The reducedorifice will restrict the volume of fluidpermitted to flow therethrough and the pressure at the'respective-end ofthe bore 71 will increase. This pressure will tend to oppose themovement of the spool 75 by the magnetic force and, when the force issufficiently diminished, will cause the spool to re- When the spool is'movedtoward either end of the bore 71, the orifice 81 at the oppositeend will be increased in eflective size and more fluid willflow throughthis orifice and be applied to the corresponding end of the main valvespool 61. This additional fluid will cause the main valve spool 61 tomove from its centered position toward the opposite end of the valvebot-e40. In 50 moving, the grooves 62, 63 in'the main valve spool willincrease the communicationbetween one 'of theinlet port 41 or 42 and themotor port 43 or 44 served thereby at thesame time increasingcommunication between the other motor porLand the exhaust port 45. Fluidfrom thepressuresource will then flow to the motor port communicatingwith the inlet port and the motor 21 will be caused to operateintherespective direction. lithe valve spool were moved in the oppositedirection,

itis obvious that the fluid motor would also operate in the oppositedirection.

When the magnetic force is reduced sufliciently and the coildeenergized, valve spool 75 will return to its centered position causingthe pilot pressure to equalize at the ends of the main spool and thiselement Will then return to its centered position. .In this position,the piston and ram of the 'hydraulic'motor will be held stationary. Itis obvious that, since the piston 23 of the hydraulic motor 21 is of thedifferential type, the main valve spool may-not occupy a truly centeredposition to hold the motor piston 23 sta- 'tionary. For purposes ofexplanation, however, such position of the mainspool will be termed acentered position. To render the main spool 61 more sensitive, it isformed with a piston portion 87 which is disposed for movement in theenlarged portion 46 of the main spool bore. The main spool has alongitudinally extending passage formed therein which communicates withtransverse passages so that pilot pressure 'from one end of the spoolwill be sup plied to the end of the piston 87 connected with the spool.The eflecvtive end areas of the spool 61 will thus beincreased to theend areas of the piston 87. A lower pilot pressure may be employed tooperate or effect the movement of the main spool 61 because of theenlarged piston 87. The flow control valve elements are normally urgedtoward an open position, that is, spaced from the valve seats 55 bycoilsprings 88 positioned between the partition 53 and the inner ends ofsockets formed in the piston valves 57. The fluid supplied to the inletport 50 will flow through the passages 47 and 48 to' the inletports orgrooves 41 and 42. When the valve spool 61 is moved and reduces thedegree of communication between either groove 41 or 42 and the adjacentgroove 62 or 63 in the spool 61, the fluid pressure will increase in thegroove 41 or 42 from which flow is obstructed. 'This fluid pressure willbe applied to the .end of the respective piston valve and will tend tomovethe valve in opposition to its spring 88. When the valve spool 61obstructs communication'between the inlet groove 41 or 42 and one of thegroove 62 or 63 in the spool, the pressure in the latter groove will bereduced, this reduced pressure being applied to the inner end of theassociated flow control piston valve 57. The differential in pressure atopposite ends of either flow control valve 57 will cause the valve tomove toward a closed position to restrict the volume of fluid admittedto the respective inlet port of the main valve. The springs 88 selectedwill determine the closing pressure of the flow control valves and,therefore, the volume of fluid supplied to the reversible fluid motor.

Thespool 75 and the coils 83 and 84 cooperate to form a .motor. Thismotor is connected with an electrical circuit illustrated in Fig. 1.This electrical circuit includes a source of direct current, indicatedby the numeral 90, and alternating current lines 91 and 92 leading froma suitable sourcerofgpower. These alternating current lines lead tocorresponding portions "of electrical coils 93 and 94, correspondingends of these'coils being connected by lines 95 and 96. The coils 93 and94 are open to receive for movement therein bars 97 and 98. The coils 93and 94 and the bars 97 and 98 form what is known in "the electrical artas a null bridge. Aslong as the bars 97 and 98 occupy arpredeterminedposition within the coils, the bridge is in balance and nopotentialbetween opposite ends thereof exists. If, :however, one of the bars isdisplaced longitudinally in either direction from the predeterminedposition, a potential is created between the opposite ends of the coils.The object herein is to make use of this potential to control theoperation of the hydraulic motor.

Line 95 .is connected .by a lead 100 with .one side of the primary coilof 'a;phase splitting transformer 101. The other end of this coil isconnected byline 102 with line.96. When one of the bars in the nullbridge is moved from its predetermined position in :one direction, a.potential "will be created which will cause a flow of current through.the coil of the transformer. This current will be of a certain phaseand will be picked up by the secondary coil 103 of the transformer. Ifthe bar in the coil has been moved in one direction, the phase ofcurrent induced in the coil 103 will cause the grid of a power amplifiertube 104 to be energized while, if the bar is moved in the oppositedirection, the coil 103 will cause the grid of another tube 105 to beenergized. When either of these grids is energized, current will bepermitted to flow from the source of direct current 90 through a line106 and through one or the other of the coils 83 and 84 (in valvemechanism 30) depending upon which of the tubes 104 and 105 isenergized, current flowing from the particular coil 83 or 84 throughline 107 or 108 to the plate of the respective amplifier tube. Thestrength of the current permitted to flow through the coil will dependupon the strength of the signal created by the null bridge.

When the null bridge is unbalanced and the signal is created, as abovementioned, the proper coil 83 or 84 of the motor will be energized andwill operate the spool 75 to supply pilot pressure to the proper end ofthe main valve spool 61 causing fluid to be directed to the fluid motor21 to make it move in the proper direction to cause the bar 97 carriedthereby to move in the same direction as the other bar was moved and tothe same extent. When bar 97 reaches a position corresponding to theposition of the bar 98, the bridge will be in balance and no potentialwill exist at that time. Bar 98 may be moved in any desired manner but,for purposes of illustration, a motor driven cam 110 has been shown inregistration with this bar. This cam will be provided with apredetermined shape to secure the desired pattern of movement of the ram24. An electric motor 111 is connected with the cam to cause itsoperation, the motor being controlled by a rheostat 112. A push buttonswitch 113 may be employed to selectively control the operation of themotor 111 or this motor may be continuously operated by closing a switch114. The spool 75 will move a distance proportionate to the strength ofcurrent supplied to the coils. It will be obvious that the volume offluid directed to the fluid motor by the main valve spool will dependupon the distance moved by spool 75. As the bar moved by the ramapproaches a position corresponding to that of the bar 98, a potentialdeveloped by the bridge will decrease and the current supplied to thetorque motor will correspondingly decrease. This current will beinterrupted when the bridge is in balance and the ram will then stopmoving.

While the form of embodiment of the present invention as hereindisclosed constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

We claim:

1. A hydraulic valve comprising a casing having a valve bore withforward and reverse motor and inlet and exhaust passages communicatingtherewith at spaced points; a reversing valve spool disposed formovement in said bore, said valve spool having flow directing meansoperative when said spool is in a predetermined position to form a flowmetering orifice between selected inlet and motor passages, said orificecreating a pressure difierential on fluid flowing from the selectedinlet to the selected motor passage; a valve element in said casing forcontrolling fluid flow through the selected inlet passage; and resilientmeans tending to move said valve element to a position to permit maximumflow through said inlet passage, said valve element being exposed onopposite surfaces and responsive to the different pressures on the inletand motor passage sides of said orifice to move in opposition to saidresilient means.

2. A hydraulic valve comprising a casing having a valve bore withforward and reverse motor and inlet and exhaust passages communicatingtherewith at spaced points; a reversing valve spool disposed formovement in said bore, said valve spool having flow directing meansoperative when said spool is in a predetermined position to form a flowmetering orifice between selected inlet and motor passages, said orificecreating a pressure difierential on fluid flowing from the selectedinlet to the selected motor passage; a valve element in said casing forcontrolling fluid flow through the selected inlet passage; resilientmeans tending to move said valve element to" a position to permitmaximum flow through said inlet passage, said valve element beingexposed on opposite surfaces and responsive to the different pressureson the inlet and motor passage sides of said orifice to move inopposition to said resilient means; and means for moving said valvespool to vary the size of said orifice.

3. A hydraulic valve comprising a casing having a valve bore withforward and reverse motor and inlet and exhaust passages communicatingtherewith at spaced points; a reversing valve spool disposed formovement in said bore, said valve spool having flow directing meansoperative when said spool is in a predetermined position to form a flowmetering orifice between selected inlet and motor passages, said orificecreating a pressure differential on fluid flowing from the selectedinlet to the selected motor passage; a valve element in said casing forcontrolling fluid flow through the selected inlet passage; resilientmeans tending to move said valve element to a position to permit maximumflow through said inlet passage, said valve element being exposed onopposite surfaces and responsive to the different pressures on the inletand motor passage sides of said orifice to move in opposition to saidresilient means; actuating means for said valve spool to vary the sizeof said orifice, said actuating means having pilot fluid passagesleading to the ends of the reversing valve spool bore; and a pilot valvefor governing fluid flow through said pilot fluid passages.

4. A hydraulic valve comprising a casing having a valve bore withforward and reverse motor and inlet and exhaust passages communicatingtherewith at spaced points; a reversing valve spool disposed formovement in said bore, said valve spool having flow directing meansoperative when said spool is in a predetermined position to form a flowmetering orifice between selected inlet and motor passages, said orificecreating a pressure differential on fluid flowing from the selectedinlet to the selected motor passage; a valve element in said casing forcontrolling fluid flow through the selected inlet passage; resilientmeans tending to move said valve element to a position to permit maximumflow through said inlet passage, said valve element being exposed onopposite surfaces and responsive to the different pressures on the inletand motor passage sides of said orifice to move in opposition to saidresilient means; actuating means for said valve spool to vary the sizeof said orifice, said actuating means having pilot fluid passagesleading to the ends of the reversing valve spool bore; a pilot valve forgoverning fluid flow through said pilot fluid passages; andelectroresponsive means for moving said pilot valve.

5. A hydraulic valve comprising a casing having a valve bore withforward and reverse motor and inlet and exhaust passages communicatingtherewith at spaced points; a valve spool disposed for movement in saidbore to alternately connect said forward and reverse motor passages withsaid inlet and exhaust passages, said valve spool having means operativewhen said spool is in position to connect selected motor and inletpassages to form a flow metering orifice between the selected passages,said orifice creating a pressure differential on fluid flowing from theinlet to the selected motor passage; fluid pressure responsive means formoving said valve spool to select the motor and inlet passages to beconnected and the location of the flow metering orifice; a plurality ofvalve elements disposed for movement in said casing to control fluidflow through the inlet passages; and resilient means tending to movesaid valve elements to positions to permit maximum flow through theinlet passages, each of said valve elements being exposed on oppositeiSllIfaCfiS :and :responsive to the pressures at the inlet 'andmotorpassage sides of a ditferent orifice to move in opposition to saidresilient means. I

-6. A hydraulic valve comprising a casing'having-a valve .bore withforward and reverse motor and inlet and exhaust passages communicatingtherewith, at spaced points; a valve spool disposed for movement in-saidbore to connect selected sets of said passages; means in said casingtending to dispose said valve spool in position to' connect all of thepassages communicating with said bore; pressure responsive means formoving said spool in-opposition to said last-named means to positions toconnect selected motor and inlet passages; means operative when saidspool is in a position to connect selected motor and inlet passages toform an orifice between the passages connected, said orifice creating apressure differential an fluid flowing from the inletto the selectedmotor passage; valve elements disposed for movement ,in said casing tocontrolfluid flow through the inlet passages; and resilient meanstending to .move ,said valve :elements to positions to a permit maximum.flow through said inlet passages, each of said valve elements beingexposed on opposite surfaces and responsive to the pressures at theinlet and motor passagelsides Of'fllfi orifice between'the inlet passagecontrolled by the respective :valvc element and the motor passageconnected therewith to movein' opposition to said resilient means.

7. Hydraulic apparatus comprising a source of fluid pressure; areversible fluid motor having amovable element; control mechanismbetween said pressure "source and said motor, said control mechanism.having a-valve casing with a bore and forward .and reverse motor andinlet and exhaust passages communicating therewith at spaced points,said motor passages communicating with said motor and said inlet passagecommunicating with said pressure source; a valve spool'disposed in saidbore 'for movement from a first position establishing communicationbetween all the passages to other positions establishing communication:between :a selected motor passage and said inlet and the other motorpassage and said exhaust; 'means normally'tending to maintain'said valvespool in the first position; means on said valve spool to cooperate withsaid casing totform an orificebetween either motor passage and the inletpassage in communication therewith, said orifice creating a pressuredifierential on fluid flowing from the inlet to theselected motorpassage;valve elements movably disposedin the inlet passages to controlfluid flow therethrough; resilient means tending to move said valveelements to positions topermit maximum'flow'through said inlet passages,said valve elements being exposed on oppositesurfaces to the pressureson he inlet and motor. passage sides of the orifices between the inletpassages andsaid motor passages andresponsive to differences in'rsuchpressures to move inopposition totsaid resilient means; fluid pressuremeans for movingtsaid valve spool :firom the 'first position :to

other positions to vary the size of saidonfices, said means having apilot valve; electro-responsive means foractuating said pilot valve,said electro-responsive means having oppositely acting solenoids; anelectrical circuit for supingtsaid pilot valve,

plying operation :current to said solenoids; and means partiallycontrolled ,by the movable element --of said ,re- 'versible fluid motorfor governing the flowof current in 'saidelectrical circuit.

8; Hydraulic apparatuscomprising agsource of fluid pressure; areversible fluid motor having a movable element; control mechanismbetween said pressure source andsaid motor, said controlmechanism'having a valve casing with a bore and forward and reversemotor and inlet and exhaust passages communicating therewith at spacedpoints, said motor passages communicating with said motor and said inletpassage communicating with said pressure source; a valvespool disposedin said bore for movementfroma first position establishing communicationbetween all the passages to other positions estal) lishing communicationbetween aselected motor passage and said inlet and the othermotorpassage and 'said exhaust; means normally tending to maintain saidvalve spool in the first position; means on said valve spoolto cooperatewith said casing to ,form an orifice between eithermotor passage and theinlet passage in communication therewith, =said orifice creating .apressure diflerential on fluid flowingrfrom the inlet to theselectedmotor passage; -valve elements movably disposed in the inletpassages to control fluid flow therethrough; resilient meanstendingtomove said valve elements .to positionsto permit maximum flowthrough said inlet passages, said valve elements being exposed onopposite surfaces to thepressures on the inlet and motor passage sides,:of the orifices between the, inlet passagesand said motor passages andresponsive to diflerences in such pressures to move 1in oppositiontotsaid resilient meanspfluid pressure means for moving said valve spoolfrom the fiIShPQSltiOll'jtO other. positions to vary-the. size of said,orifiees, said means havinga pilot valve; electro-responsive means foractuatsaid electro-responsive meanshaving oppositely actingsolenoidsresponsive tothestrengthof current supplied thereto to determinethedirection and extent of movement of. Said 'pilot -valve;-an electricalcircuit forsupplyingoperatingcurrent to said solenoids; and

means in said circuit operated ,in part by thermovable element of saidfiuidmotor and in partby aselectively actuated element for varying thestrength of current supplied to said solenoids.

References Cited in the file of this patent UNITED STATES PATENTSGermany May 7, 1931

